High performance cyanate-bismaleimide-epoxy resin compositions for printed circuits and encapsulants

ABSTRACT

A thermosetting resin system including an epoxy resin, a bismaleimide, a cyanate ester and a co-curing agent that is an aromatic moiety having unsaturated aliphatic groups and glycidyl ether groups is provided. Preferred co-curing agents are 2-allylphenyl glycidyl ether and 2,2′-diallylbisphenol A diglycidyl ether. The resin system can be employed as an encapsulant for electronic components and as dielectric layers with microvias on printed circuits.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation in part which claims priorityto U.S. patent Applications Ser. Nos. 08/949,204, filed on Oct. 10,1997, and 08/949,214, filed on Oct. 10, 1997, which are incorporated byreference. This CIP also claims priority to U.S. Provisional ApplicationSer. No. 60/135,356, filed on May 21, 1999, which is also incorporatedherein by reference.

[0002] The U.S. Government has a paid-up license in this invention andthe right in limited circumstances to require the patent owner tolicense others on reasonable terms as provided for by the terms ofcontract no. DASG 60-97-M-0072 awarded by Ballistic Missile DefenseOrganization.

FIELD OF THE INVENTION

[0003] This invention relates generally to printed circuits orencapsulated electronics devices, such a silicon chips, coated withcurable resin compositions comprising epoxy resins, cyanate esters,bismaleimides, and a co-curing agent.

BACKGROUND OF THE INVENTION

[0004] The fabrication of electronic printed circuits often requires thefabrication of very fine electrical interconnections, that are as smallas 50 microns in diameter, through a dielectric resin. This technologyis generally known as microvia technology. Also, in the fabrication offlip chips, ball grid arrays (BGAs) and chip-scale packages, it isnecessary to create electrical interconnections in the form of tinyballs or joints with solders or other electrically conductivesubstances. Generally the electrical interconnections are encapsulatedin a non-conductive permanent resin. The properties of the resin chosenfor microvia and encapsulated interconnections are critical to thereliability to the electrical device. A number of resins have been usedfor such applications, such as epoxy resins, acrylates, cyanate estersand bismaleimide-triazine-epoxy resins.

[0005] Epoxy resins, which represent some of the most widely usedresins, are characterized by easy processability, good adhesion tovarious substrates, high chemical and corrosion resistance, andexcellent mechanical properties. However, epoxy resins have relativelypoor performance at high temperatures, have high dielectric constants,and exhibit significant water absorption. Epoxy resins are generallycured by arnines and anhydrides. The cured materials typically containrelatively large proportions of hydrophilic groups such as hydroxylgroups which increase water absorption. Epoxy resins thus are sensitiveto hydrolysis at high temperature and high humidity. Moreover, thechemical resistance of epoxy resin is not as good as that of cyanateesters and bismaleimides.

[0006] Cyanate ester resins have improved performance relative toconventionally cured epoxy resins. Polyfunctional cyanate esters arenormally needed to achieve high crosslinking densities and high glasstransition temperatures (Tg). Unfortunately, polyfunctional cyanateesters are typically solid or semi-solid at ambient temperatures andthus the formulated resin systems have relatively high viscosities.These resin systems often require significant amounts of solvents.

[0007] Another leading thermosetting resin is bismaleimide which ischaracterized by excellent physical property retention at hightemperatures and high humidities and stable (non-fluctuating) electricalproperties over a wide temperature range. These properties makebismaleimide particularly suitable for advanced composites andelectronics. Bismaleimides are capable of good performance attemperatures of up to about 230° C. to 250° C. with good hot-wetperformance. However, bismaleimide homopolymers are brittle and as aresult are susceptible to microcracking. Moreover, the chemicalresistance of bismaleimides is poor in the presence of base compounds.Generally, bismaleimide is combined with cyanate ester to create a resinclass generally known as BT resins. These resins provide improved glasstransition temperature performance and other improved properties ascompared to epoxy resins. They are also less expensive than cyanateester resins. However, the mixture of cyanate esters and bismaleimidesexhibits little co-polymerization, therefore, the combination hasinferior properties compared to pure cyanate ester or bismaleimideresins.

[0008] The art is in need of thermosetting resins demonstrating bothhigh temperature performance and improved physical toughness, especiallyfor microvia and encapsulated electrical interconnect electronicsapplications, such as printed circuits, flip chips, BGAs and chip scalepackages.

SUMMARY OF THE INVENTION

[0009] This invention relates to a resin system comprising a mixture ofepoxy resins, bismaleimides, cyanate esters and low viscosity co-curingagents that can be applied to a printed circuit, a silicon chip orwafer, or other electronic component, encapsulating it with adielectric. Openings can be created in the encapsulating resin byconventional methods such as laser drilling, photoimaglng, plasma, orother techniques known in the art. These openings can be metallized toform highly reliable electrical interconnections. The inventive resinsystem demonstrates the excellent processability, adhesion, chemical andcorrosion resistances, and mechanical qualities normally associated withepoxy resins; the system also exhibits superior physical and chemicalproperties as well as the stable electrical properties associated withbismaleimides and cyanate esters. All of these are highly desirablecharacteristics for encapsulants, microvia and interconnectionapplications.

[0010] In one aspect the invention is directed to a curable compositionthat includes:

[0011] (a) a cyanate ester;

[0012] (b) a bismaleimide;

[0013] (c) a co-curing agent having the structure R¹—Ar—R² wherein Ar isat least one unsaturated aromatic carboxylic moiety, R¹ is at least oneunsaturated aliphatic moiety and R¹ is at least one epoxide moiety withthe proviso that when two or more unsaturated aromatic carboxylicmoieties are present, at least one of the unsaturated aromaticcarboxylic moieties has an unsaturated aliphatic moiety and an epoxidemoiety attached thereto;

[0014] (d) an epoxy resin;

[0015] (e) optionally, a free-radical initiator; and

[0016] (f) optionally, a cyanate ester trimerization catalyst.

[0017] Preferred curing agents are 2-allylphenyl glycidyl ether and2,2′-bis (3-ally-4-glycidoxy phenyl) isopropylidene, hereinafterreferred to as 2,2′-diallylbisphenol A diglycidyl ether.

[0018] The co-curing agent reacts with the cyanate ester, epoxy resinand bismaleimide. The viscosity of the co-curing agent is low enough atroom temperature so that no solvent is generally necessary. Thecrosslinking density of the cured composition can be varied over a widerange by adjusting the relative proportions of each component in theresin mixture.

[0019] The invention is based in part on the integration of (i) aglycidyl group, which is reactive with cyanate ester, and (ii) anunsaturated aliphatic group such as an allyl group, which is reactive tobismaleimide, into a co-curing agent molecule. The presence of thisco-curing agent in the inventive resin system not only makes it possibleto co-cure cyanate ester and bismaleimide, in addition, it reduces theviscosity of the resin system because of the low viscosity of theco-curing agent. Furthermore, the combination of epoxy resin with thecyanate ester by means of well-established curing reactions produces acured composition with the before mentioned desirable properties. Forexample, the thermal stability, high temperature performance and hot-wetresistance of the cured inventive resin system are superior to those ofconventional amine and anhydride cured epoxy resins. In addition, theuncured resin exhibits excellent processability while the cured resinsystem demonstrates toughness and chemical resistance that are superiorto those from bismaleimide or cyanate ester homopolymers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 are tan delta dynamic mechanical analyzer (DMA) scans fromtwo resin mixtures showing the glass transition temperatures of two testresin mixes, one with and one without the co-curing agent APGE;

[0021]FIG. 2 is the thermogravimetric scans for a cyanateester-bismaleimide-epoxy resin mixture with APGE;

[0022]FIG. 3 are thermal decomposition weight loss scans for (i) resinshaving APGE (ii) resins having DADE, and (iii) FR-4 epoxy laminate;

[0023]FIG. 4 is the DMA scan of an inventive resin composition;

[0024]FIG. 5 is the DMA scan of an inventive resin composition;

[0025]FIG. 6 is the thermal mechanical analyzer scan of same inventiveresin composition of FIG. 5;

[0026]FIG. 7 are differential scanning calorimetry scans ofbismaleimide-co-curing agent mixtures with and without a free-radicalinitiator;

[0027]FIGS. 8, 9, and 10 illustrate encapsulation of an electronicdevice with a resin composition; and

[0028]FIGS. 11, 12, and 13 illustrate encapsulation of a printed circuitboard with a resin composition.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention is based in part on the development of aresin system comprising cyanate ester resins, bismaleimides, co-curingagents and epoxy resins. The co-curing agent comprises two differentreactive groups: (i) a moiety having an unsaturated aliphatic groupcapable of reacting with bismaleimides, e.g., an allyl group, and (ii) aglycidyl ether, that is capable of reacting with cyanate esters. Thephysical properties of the pre and post cured inventive resin system canbe varied by employing different proportions of cyanate esters, epoxyresins, bismaleimides, and co-curing agents. Advantageouscharacteristics of the inventive resin system include, for example:

[0030] 1. Processability that is comparable to epoxy resins and curesupon heating, with the cured product overall performing better thaneither cyanate esters, epoxy resins or bismaleimides individually.

[0031] 2. Good thermal stability, up to about 350° C., and demonstratingglass transition temperatures from 200° C. to 260° C., depending on theproportion of bismaleimides and cyanate esters used in the inventiveresin system.

[0032] 3. No volatiles are evolved from the curing reaction and thusvoid-free cured compositions are produced.

[0033] 4. Improved adhesion properties compared to bismaleimides orcyanate esters.

[0034] 5. The hot-wet performance of the cured composition is muchbetter than that of conventionally cured epoxy resins.

[0035] 6. The integration of epoxides and carbon-carbon double bondsinto the co-curing agent makes the resins polymerizable bylight-initiated free-radical catalysts. This will allow creation ofencapsulants that can be polymerized by ultraviolet or electron beamexposure, either in bulk or through a mask to produce photodefinedfeatures and microvias.

[0036] 7. Cost effective alternative to prior art-epoxy resin, cyanateester and bismaleimide resins for industrial dielectrics andencapsulants.

[0037] Co-curing Agent

[0038] The co-curing agent has the structure R¹—Ar—R² where Ar comprisesis at least one aryl moiety, R¹ is at least one unsaturated aliphaticmoiety and R² is at least one glycidyl ether moiety. Ar preferably hasone aryl moiety but it is understood that it can comprise multiplearomatic moieties linked linearly (e.g. a novolac), or by branching(e.g. triphenyl, tetraphenyl). Preferably each aryl moiety has at leastone of (i) an unsaturated aliphatic moiety and (ii) a glycidyl moietyattached thereto, with the proviso that the co-curing has at least oneof each moiety. The number of aromatic moieties in Ar is typically lessabout than 3. When more than one aryl moiety is present, they are linkedby suitable divalent groups such as, for example, a low alklylene,—(CH₂)_(n)— where n is 1-6, preferably 1-3, and more preferably 1. Theterm “aryl” refers to an unsaturated aromatic carbocyclic group of 6 to14 carbon atoms having a single ring (e.g., phenyl) or multiplecondensed rings (e.g., naphthyl or anthryl). Preferred aryls includephenyl, naphthyl and the like. Preferred co-curing agents have structureI or II:

[0039] where each of R¹ and R² is preferably H, CH₃ or CF₃. Bothstructures can be further substituted with, for example, lower alkylshaving preferably 1-6 carbons more, preferably 1-3 carbons and halidesCl, Br or F. Particularly preferred co-curing agents are 2-allylphenylglycidyl ether (APGE), and 2,2′-diallylbisphenol A diglycidyl ether(DADE) which have the following structures III and IV, respectively:

[0040] APGE and DADE can be synthesized in accordance with the followingwell-established reaction mechanism:

[0041] Cyanate Esters

[0042] Suitable cyanate esters are polyfunctional molecules or oligomershaving at least two —OCN groups. Cyanate esters are self reactive andalso cure in the presence of epoxy resin or bismaleimide. Suitablepolyfunctional cyanate esters are described, for example, in U.S. Pat.Nos. 4,831,086, 5,464,726, 4,195,132, 3,681,292, 4,740,584, 4,745,215,4,776,629 and 4,546,131, which are incorporated herein. Preferredpolyfunctional cyanate esters include the following:

[0043] where x is any suitable divalent moiety, such as —O—, a loweralkylene —(CH₂)_(m)— where m is 1-6, preferably 1-3, and most preferably1,—CH₃CH₂—, —CH₃CH₃CH₂—, or other functional divalent group. A preferredpolyfunctional cyanate ester used for its superior dielectric propertiesis:

[0044] where n is an integer from 0 to 200 and preferably from 0 to 1.Typically in commercial resins n has an average value of about 0.4. Thepolyfunctional cyanate serves to increase the density of cured resincomposition. The polyfunctional cyanates react with the epoxy resin andthe epoxide group in the co-curing agent thereby forming crosslinkedpolymeric networks. Polyfunctional cyanate esters are typically solid atambient temperatures (25° C.) but dissolve readily in the co-curingagent and the epoxy resin, although some warming may be needed to bringabout solution.

[0045] Epoxy Resins

[0046] Suitable epoxy resins include any of a variety of polyfunctionalepoxy resins that are known or commercially available. Suitable epoxyresins are described, for example, in U.S. Pat. No. 5,464,726, which isincorporated herein. Preferred commercially available epoxy resinsinclude, for example, bisphenol A epoxy resins, e.g. Shell EPON 800series, bisphenol F, epoxy novolac, epoxy cresol novolac,N,N-diglycydyl-4-glycidoxyaniline, and4,4′-methylenebis(N,N-diglycidylaniline). Other exemplary commerciallyavailable epoxy resins are available as Dow Tactix 742, Shell RSL-1107,EPON 825, EPON 828, EPON 1031, SU-3, SU-8, and Ciba-Geigy AralditeLT8011, LT8052, LT8047, CY8043, CY179, and Dow DEN438 and DEN 439.

[0047] Bismaleimides

[0048] The generalized structure of bismaleimide is:

[0049] where R is any suitable divalent functional moiety such as, e.g.,a lower alkylene —(CH₂)_(m)—, where m is 1-6, preferably 1-3, and mostpreferably 1. A preferred divalent functional moiety is:

[0050] Suitable bismaleimides are further described, for example, inU.S. Pat. Nos. 5,464,726 and 4,978,727, which are incorporated herein. Apreferred bismaleimide is MDA Bismaleimide Resin 5292A from Ciba Geigy.

[0051] Free Radical Initiators

[0052] There are two preferred types of free radical initiators: heattriggered initiators and energetically-triggered initiators. Examples ofheat triggered initiators are lauryl peroxide and tert-butyl peroxide.Heat triggered initiators operate by decomposing at the triggertemperature, thereby creating free radicals as follows:

[0053] The free radicals then initiate chain growth polymerization ofthe unsaturated bonds in the bismaleimide and the co-curing agent, asillustrated by the following example reaction:

[0054] The newly formed free radical continues the chain reation.

[0055] Similarly, energetically-triggered initiators also produce freeradicals which initiate the chain growth polymerization of unsaturatedbonds in the bismaleimide and the co-curing agent. However, these aretriggered by actions of energetic photons, as from an ultraviolet lightsource, or electrons, as from a plasma or electron beam, instead of byheat.

[0056] Typically, the free radical initiator agent, when employed,comprises about 0.1% to 3%, preferably 0.1% to 2% and more preferably0.5% to 1.5% by weight of the curable composition.

[0057] Polymerization

[0058] Cyanate esters can homopolymerize to produce symmetrical arylcyanurate rings:

[0059] where Ar groups are aryl groups. Cyanate esters and epoxidesco-polymerize through a complex series of rearrangement and substitutionreactions, forming heterocyclic 5- or 6-membered rings. Specificexamples include oxazoline rings and oxazolidinone rings:

 O—Ar′

[0060] where Alk═—CH₂—CH—CH₂—O—Ar″ and where Ar′ and Ar″ are aromaticgroups resulting in good thermal stability and improved moisture andchemical resistance.

[0061] Bismaleimides are known to free-radical polymerize with heat,with or without the presence of free radical initiators, as follows:

[0062] The reactions between a maleimide group and an allyl-substitutedbenzene is also well known—the Ene reaction and subsequent Diels-Alderreactions, as illustrated as follows:

[0063] The above reactions demonstrate that compounds having an aromaticring structure that have an allyl group and an epoxide group attachedthereto are effective co-polymerizers for both cyanate esters andbismaleimides, to form numerous cycloaliphatic polymers. These polymersare quite stable against water and other chemicals, mechanically toughand resistant to high temperature decomposition. Importantcharacteristics afforded by the degree of crosslinking in the polymermatrix formed are the low coefficients of thermal expansion and highglass transition temperatures that can be attained. These are essentialproperties for encapsulants in electronics applications. The absence ofhydroxyl groups in the polymer matrix also implies significantly lowerdielectric constant for the polymers as compared to conventionally curedepoxy resins. Incorporating epoxy resins into the polymer also providesfor improved adhesion of the polymer to surfaces as compared to purecyanate esters and/or bismaleimide resins. This combination of improvedcharacteristics-lower dielectric constant, lower thermal expansion,higher glass transition temperature, better toughness, lower waterabsorption, better chemical resistance, better adhesion and higherdecomposition temperature—is essential for producing printed circuitryand encapsulants for silicon and other electronic devices.

[0064] Another important characteristic of the co-curing agents is thatthey are generally very low viscosity liquids at or near roomtemperature so they function as excellent solvents for the cyanateesters and bismaleimides. Alone, or in combination with liquid epoxyresins, the co-curing agents dissolve the cyanate esters andbismaleimides to form room temperature or hot melt liquid resin mixturesthat are completely free of volatile solvents. This is an importantproperty in the fabrication of encapsulants and microvia dielectriclayers as it permits creation of liquid pastes and resins that can beapplied in relatively thick layers to electronic components in one stepand cured without evolution of volatile solvents that create voids.

[0065] Although volatile organic solvents are typically not employed, inapplications where the presence of volatile organic solvents is not aproblem, solvents can be added if desired. Such solvents include, forexample methyl ethyl ketone, chloroform, methylene chloride, acetone,and 1-methyl 2-pyrrolidinone.

[0066] Another significant advantage of the inventive resin compositionis that the addition of free-radical polymerization initiators createsresin systems that can be multistage-cured. This allows application ofthe resin composition in liquid form, which is subsequently hardened byheat or ultraviolet light. The use of a thermally-initiated,low-temperature triggered free radical initiator, such as laurylperoxide, allows polymerization to be initiated at a temperature betweenabout 100°-130° C. A resin composition comprising such an initiator canbe used to coat an electronic component or circuit board with a liquidencapsulant that is then partially cured by heating to the initiatortrigger temperature. This creates a partially polymerized solid, which,though not completely polymerized, will no longer flow like alow-viscosity liquid. Such a resin composition can be applied by screenprinting, curtain coating or other method known to one skilled in theart. The coated component or circuit can then be heated rapidly to atemperature at which the free radical polymerization can occur tocomplete the polymerization.

[0067] The use of a pre-cured or partially cured resin compositionallows easy post processing by means of laser or plasma etching, twocommon methods used in the creation of microvias. The low polymerizationdensity of the polymer at this first stage of curing allows very rapidand low-energy laser drilling and plasma etching to occur, therebygreatly speeding up the laser drilling process. This providessubstantial advantages in the manufacture of microvia components wherespeed translates into significant cost and manufacturing advantages.

[0068] Another approach to free radical polymerization is to use anultraviolet sensitive photoinitiator. Instead of heat, radiation (e.g.,electrons or ultraviolet light) is used in the first stage of curing andsolidifying the liquid resin composition. After this firstlight-initiated cure, the coated part can be laser or plasma drilled aspreviously indicated.

[0069] The photoinitiator induces a chain reaction or chain growthpolymerization of unsaturated carbon-carbon bonds. This type of curingis effective for achieving a first stage crosslinking for photoimaging.When a layer of material is exposed to the UV light through a mask, ithardens. The mask can be made of any suitable UV blocking/absorbingmaterial with openings through which UV radiation can be transmitted.The non-exposed portions of the resin composition will form themicrovias which typically have a diameter of about 20 μm to 200 μm. Anyunexposed resin composition can then be dissolved away, leaving theimage of the mask. Then the image can be completely hardened with heat.The polymer can be applied in thin coats or layers that can be instantlyUV-cured to a gel-set by the UV light initiated reaction. The unexposedresin composition can then be washed away with a suitable solvent.Finally heat is applied to effect a deep and complete cure of thepolymer resin.

[0070] This gives rise to yet another approach to using free radicalpolymerization to produce photo-defined microvias. In this case, theresin composition is prepared as a viscous liquid and is then applied toan electronic component or printed circuit board. A very high viscositycomposition is preferred since it will remain in place withoutpolymerization while the ultraviolet light is used to image themicrovias through a photomask. This selective exposure produces someregions in the resin which are cured partially and other regions whichare completely uncured by being masked from the ultraviolet light by thephotomask.

[0071] Subsequent to exposure to ultraviolet light through thephotomask, the coated component or printed circuit board is developed inan aqueous or organic solution of KOH. The developer dissolves theunexposed resin regions away, leaving behind the ultraviolet polymerizedportions of the resin on the component or printed circuit board. Afterdevelopment, microvias are present in the resin system. This allows arapid and inexpensive way to fabricate many microvias at one time usingsimple photo exposure techniques. Subsequent full hardening of the resinoccurs by heating the coated component, with its microvias, to the finalcuring temperature of the resin to produce a fully polymerized polymerwith its final ideal properties. For this reason, a combination of heatand UV is most effective for photoimaging.

[0072] Formulation of Resin Compositions

[0073] Both APGE and DADE are liquids at room temperature and easy toformulate with cyanate/epoxy/bismaleimide resins. It should be notedthat during storage the components of the resin composition will slowlyreact. Therefore, the term “epoxy resin” include partial or prepolymersthereof. Similarly, for “bismaleimide,” and “co-curing agent” each terminclude partial or prepolymers thereof.

[0074] In formulating the inventive resin compositions, it is importantto recognize that cyanate ester and bismaleimide are each capable ofself-polymerization. As a result, the concentrations of cyanate esterand bismaleimide can each vary from 1 to 99% of the molar concentrationof the resin composition and still achieve complete polymerization. Onthe other hand, the epoxy resin which does not self-polymerize, needsthe cyanate ester for the reaction to occur. In determining the maximumepoxy resin concentration, it is necessary to account for the epoxide inthe co-curing agent as this reactive group also will consume cyanateesters during polymerization. As a result, to achieve substantially fullpolymerization, the epoxide molar equivalent concentration in the resincomposition, which includes the co-curing agent and the epoxy resin, ispreferably equal to or less than the cyanate ester molar equivalentconcentration. Likewise, since the co-curing agent reacts with thebismaleimide, the co-curing agent concentration is preferably less thanthe lesser of the cyanate ester or the bismaleimide molar equivalentconcentrations. Any resin composition prepared within these“proportional” limitations, will provide a fully polymerized polymerwhen cured.

[0075] To minimize the amount of costly cyanate ester and bismaleimideused without significantly adversely effecting the final properties ofthe resin composition, for a preferred embodiment of the resincomposition, the cyanate ester comprises about 3 to 5 molar equivalentparts of the composition, the epoxy resin comprises 1.5 to 5 molarequivalent parts of the composition, the bismaleimide comprises 0.5 to1.5 molar equivalent parts of the composition and the co-curing agent0.5 to 1.5 molar equivalent parts of the composition, subject to theabove proportional limitations. It should be noted that the above molarequivalent proportions are based on resin compositions containing nosolvents, catalysts, fillers, e.g., silica, or free-radical initiators,which are optional. More preferred are resin compositions comprisingthese proportions and also comprising 100 to 500 parts per million ofcyanate ester weight of a cyanate catalysts such as copper (II) acetylacetonate.

[0076] Particularly, preferred resin compositions are those that arestoichiometrically balanced and which use minimal amounts of co-curingagent and bismaleimide. Subject to the above proportional limitations,preferred resin compositions include 5 to 6 molar equivalent partscyanate ester, 1.5 to 5 molar equivalent parts epoxy resin, 200 to 400parts per million of cyanate ester equivalent of a cyanate catalystssuch as copper (II) acetyl acetonate catalyst, and 0.75 to 1.25 molarequivalent parts each of bismaleimide and co-curing agent, with theproportions of bismaleimide and co-curing agent being equal.

[0077] In formulating the resin composition, the components are mixedand heated in order to melt the bismaleimide and the polyfunctionalcyanate ester which are solids. Typically, the mixture is heated to atemperature range of about 70° C. to 115° C. until the mixture is aliquid. If desired, a solvent such as methyl ethyl ketone or acetone canbe added to the formulation to facilitate process ability.

[0078] To insure a homogenous resin composition and to reduce loss ofthe co-curing agent through evaporation during the cure cycle, theco-curing agent and the bismaleimide monomers can be first pre-reacted.This can be done by stirring the two components under heat at about 115°C. for four or five hours. This pre-reaction causes the allyl in theco-curing agent and the bismaleimide to co-react, forming a light slurrywhich readily dissolves with the cyanate ester and the epoxy duringresin mixing.

[0079] The inventive resin composition can be cured by heat. The curingtemperature range is from about 100° C. to 250° C., more preferably from130° C. to 225° C. and most preferably from 150° C. to 220° C. In apreferred method, the system is initially cured at a lower temperatureof about 120° C. to 140° C. for about 2 hours and is followed by postcuring treatment (at 210° C. to 230° C.) for another hour. The curedresins have high glass transition temperatures ranging from 200° C. to250° C., depending on the component ratios; and the cured resins alsoexhibit thermal stability against decomposition to a temperature of atleast between 350° C. and 400° C. In addition, the effectively tailoredproperties from epoxy and bismaleimide include the good adhesionproperties, chemical resistance, low water absorption and high heatdistortion temperature.

[0080] A catalyst for trimerization of the cyanate ester is required.Acetylacetonates of various transition metals, e.g., Cu, Co, Zn, can beemployed at very low concentrations, e.g., a few hundred parts permillion.

EXAMPLES Example 1

[0081] (Synthesis of 2-allylphenyl Glycidyl Ether)

[0082] APGE was synthesized from 2-allyl phenol (AP) and epichlorohydrin(EPH) in the presence of aqueous sodium hydroxide at 115° C. undernitrogen. The reaction was optimized by using 10 times excess (molarratio) of EPH and minimizing water in the reaction. During the reaction,water was produced by the reaction between 2-AP and EPH. Since water andEPH form an azeotrope, water was removed from the reaction by azeotropicdistillation, which also drives the reaction forward. Collected EPH wasreturned as needed to the mixture to prevent undesirable side reactions.After 4 hours, the resultant salts were separated from the product. Theproduct was then purified by extraction of the oil phase with toluene,followed by removal of excess EPH and aqueous phase with toluene, whichwas also used as an azeotropic agent. The product obtained was a thin,yellowish, transparent liquid. Yield was about 90%. Distillation at lowpressure (0.3 mm of Hg) yielded a water white mobile liquid with aboiling point of 72-72° C. Atmospheric distillation produced a boilingpoint of 272-274° C.

Example 2

[0083] (Synthesis of 2.2′-diallylbisphenol A Diglycidyl Ether)

[0084] To synthesize DADE, 2,2′-diallylbisphenol A was added to 20 timesexcess (molar ratio) epichlorohydrin (EPH). The reaction temperature wasraised to about 115° C. under nitrogen and aqueous sodium hydroxide wasadded slowly. As in the APGE synthesis of Example 1, water was removedfrom the reaction by azeotropic distillation, which also drives thereaction forward. Collected EPH was returned as needed to the mixture toprevent undesirable side reactions. After the reaction was completed, in4 hours, the salts were filtered from the product. The product was thenpurified by extraction of the oil phase with toluene followed by removalof excess EPH and aqueous phase with toluene. The product obtained wasyellowish viscous liquid.

[0085] FTIR results supported complete reaction and the purity of theproducts, based on the presence of the peaks at 1234 and 1127 cm⁻¹(ether) and 920 cm⁻¹ (allyl) and others. Elemental analysis alsoconfirmed the formation of the products.

Example 3

[0086] (Cured Resin Composition 1)

[0087] To demonstrate the effect of the co-curing agent APGE, two resinmixtures, one containing APGE and the other without were tested. Themolar equivalent ratios of the two mixtures included:

[0088] 1. 1 part B-10 cyanate ester resin from Ciba-Geigy.

[0089] 2. 1 part 1,l-(methylene di-4,1-phenylene) bismaleimide fromAldrich.

[0090] 3. (i) 0.2 or (ii) 0 parts APGE curing agent.

[0091] For clarity in this demonstration, the epoxy resin was omitted.The mixtures were cured in accordance with the following cure cycles:125° C. for 2 hours, 150° C. for 1 hour, 175° C. for 2 hours, 200° C.for 2 hours, and then 250° C. for 2 hours. No attempt was made tooptimize the cure cycles. After the first cure period at 125° C., ahomogenous, transparent solid was observed. Dynamic mechanical analysis(DMA) scans of tan delta of the two cured compositions are in FIG. 1.Note that without the APGE, the glass transition temperature isbifurcated, whereas the APGE-containing sample has a single high glasstransition. This suggests that the APGE is acting as a bridge betweenthe cyanate ester and the bismaleimide. Without the APGE, the two DMApeaks suggest the presence of two independent interpenetrated polymernetworks. However, with the APGE, these two networks are apparentlybridged together, forming one single polymer with a single high glasstransition.

Example 4

[0092] (Cured Resin Composition 2)

[0093] To demonstrate thermal characteristics, two resin mixtures wereprepared and they included:

[0094] 1. 3 molar equivalent parts epoxy resin (SU-3 from Exxon).

[0095] 2. 6 molar equivalent parts B-10 cyanate ester resin fromCiba-Geigy.

[0096] 3. 0.5 molar equivalent parts 1, 1-(methylene di-4,-phenylene)bismaleimide from Aldrich.

[0097] 4. (i) 0.5 molar equivalent parts 2-allyl phenyl glycidyl ether,or (ii) 2,2′-diallyl bisphenol A diepoxide co-curing agent.

[0098] 5. 0.5 cyanate weight percent of copper (II) acetyl acetonatecatalyst.

[0099] The non-optimized curing cycle for the two mixtures was: 2 hourat 125° C., 2 hours at 150° C., 1 hour at 175° C., 2 hours at 200° C.DMA scans of tan delta for the APGE mixture are shown in FIG. 2,indicating this mixture had a glass transition at 220° C. The DMA scansof the DADE mixture were very similar. FIG. 3 shows thethermogravimetric scans for the two resins, compared with epoxy FR-4glass laminate. As is apparent, the glass transition of the FR-4 occursat less than 150° C. The resins clearly deliver superior thermalproperties compared to conventional epoxy resin.

Example 5

[0100] (Cured Resin Composition 3)

[0101] To demonstrate thermal characteristics of high epoxy-contentresin compositions, a resin mixture was made with the followingcomponents:

[0102] 1. 5 molar equivalent parts epoxy resin (SU-3 from Exxon).

[0103] 2. 4 molar equivalent parts B-10 cyanate ester resin fromCiba-Geigy.

[0104] 3. 0.5 molar equivalent parts 1,1-(methylene di-4, 1-phenylene)bismaleimide from Aldrich.

[0105] 4. 0.5 molar equivalent parts 2,2′-diallyl bisphenol A diglycicylether (DADE) curing agent.

[0106] 5. 0.5 cyanate weight percent of copper (II) acetyl acetonatecatalyst.

[0107] The curing cycle for the mixture was: 2 hours at 125° C., 2 hoursat 150° C., 1 hour at 175° C. and 2 hrs at 200° C. In FIG. 4, dynamicmechanical analyzer scans of the cured composition indicate that theglass transition temperature is 242° C.

Example 6

[0108] (Cured Resin Composition 4)

[0109] In this example, the bismaleimide and APGE were “pre-staged” tominimize loss of the APGE during curing. Equimolar quantities of CIBA5292A and APGE were pre-mixed. This mixture was co-reacted in a metalcan for four hours in a forced-air oven, at about 113° C. with continualstirring to produce the bismaleimide-APGE co-reactant. The 113° C.temperature was selected to insure safety when staging large batches ofthis combination of reactants. During this period the initially heavyslurry was transformed to a still heterogeneous but much lower viscositycondition. After cooling to room temperature, the slurry readilydissolved in cyanate resin mixed with epoxy resin. No precipitation ofthe bismaleimide occurs upon mixing. The mixture showed no changes invisible characteristics at room temperature over long periods of time.

[0110] A resin composition was mixed with the following molarproportions:

[0111] 1. 5 molar equivalent parts epoxy resin (Shell Epon 826B).

[0112] 2. 4 molar equivalent parts B-10 cyanate ester resin fromCiba-Geigy.

[0113] 3. 4 molar equivalent parts B-30 cyanate ester resin fromCiba-Geigy.

[0114] 4. 1 molar equivalent part of the bismaleimide-APGE co-reactantproduced above.

[0115] 5. 0.5 cyanate weight percent of copper (II) acetyl acetonatecatalyst.

[0116] To establish acceptable thixotropy, a flow control agent, CABOSILPTG (a high-surface area silica) was added. For coupling the resinmatrix to the particulate surface, a surface finish agent for the flowcontrol agent, Z-6040 (Dow Corning), was also employed. The finish agentis an epoxy-containing monomer which couples the silica through theepoxy by co-reacting with the cyanate groups in the resin. To the abovemixture was added 5 wt % CABOSIL PTG followed by an additional 0.5 wt %of Dow Z-6040 epoxy silane (trimethoxyglycidoxypropyl silane). Ahigh-shear blender was used to disperse the powder. The finalcomposition consisted of a thixotropic paste that could be readilyscreen printed through a 100 mesh screen.

[0117] The curing cycle for the mixture was: 2 hours at 125° C., 2 hoursat 175° C., 2 hours at 200° C. then 1 hour at 225° C. and finally 1 hourat 250° C. In FIG. 5, dynamic mechanical analyzer scan of thecomposition indicates that the glass transition temperature is 213° C.In FIG. 6, the cured resin's thermal mechanical analyzer scan is shownto have a coefficient of expansion of about 42 ppm/° C. below the glasstransition temperature.

[0118] The paste produced in this example was screen printed onto asilicon wafer with a 100 mesh screen and cured per the above cure cycle.The resultant encapsulant was observed to encapsulate the waferuniformly and without voids or bubbles.

Example 7

[0119] (Cured Resin Composition 5)

[0120] Depending on the initiator used, the reactions betweenbismaleimide and the co-curing agent allyl groups can occur at as low as100° C. To demonstrate the effect of heat initiated free-radicalinitiators, two representative resin mixtures were made, one containinga free-radical initiator and the other without. The resin compositionsof the mixtures included:

[0121] 1. 1 molar equivalent part 1,1-(methylene di-4,1-phenylene)bismaleimide from Aldrich.

[0122] 2. (i) 1 molar equivalent part 2-allyl phenyl glycidyl ether inmixture 1 or (ii) 2,2′-diallyl bisphenol A diglycidyl ether (DADE) inmixture 2.

[0123] 3. (i) 1 wt % lauryl peroxide free radical initiator in mixture 1and (ii) no peroxide in mixture 2.

[0124] To simplify the differential scanning calorimetry (DSC) data anddemonstrate the free radical's effect clearly, other resin componentswere omitted. FIG. 6 illustrates the effect of the free radical. The topDSC scan is for the mixture without the free radical initiator while thebottom scan is for the mixture with the initiator. Comparing the twoscans, the second exotherm that peaks at about 370° C. in the top scanis observed to be unaffected by the free radical by appearing in bothscans. However, the two exotherms that peak at about 250° C. in theupper scan have disappeared and have been replaced with a new exothermat 102° C. in the bottom scan. The lower temperature exotherms in bothscans are attributed to the polymerization of the bismaleimide throughits unsaturated carbon double bonds with itself and with the allylgroups in DADE. The significant shift in the polymerization temperaturefor this reaction is due to the free radical initiator. Using otherperoxides that trigger at higher temperatures, it was observed that thisexotherm peak shifts according to the initiator's trigger temperature.

Example 8

[0125] (Cured Resin Composition 6)

[0126] In free radical photocurable resin compositions, thephotoinitiator absorbs UV radiation followed by a subsequent reaction togive a free-radical initiator. A photoinitiator, IRACURE 369 from CibaSpecialty Chemical, was mixed with a representative resin mixture thatincluded:

[0127] 1. 2 molar equivalent parts epoxy resin (SU-3 from Exxon).

[0128] 2. 3 molar equivalent parts B-10 cyanate ester resin fromCiba-Geigy.

[0129] 3. 1 molar equivalent part 1,1-(methylene di-4,1-phenylene)bismaleimide from Aldrich.

[0130] 4. 1 molar equivalent part 2-allyl phenyl glycidyl ether or2,2′-diallyl bisphenol A diepoxide co-curing agent.

[0131] 5. 5 weight % IRACURE 369 from Ciba Specialty Chemical.

[0132] A thin layer of the photosensitive resin composition from achloroform solution (i.e., 2 ml/2 g concentration) was applied to anepoxy printed circuit boards. The thickness of the layer was notcarefully controlled, but was about 0.001 in thick. After exposurethrough a mask to a long wave UV lamp (100 Watt) for 15 minutes or so ata distance of about 1 inch, the “image” was developed by using either anacetone/water mixture (5 volume parts acetone to 1 volume part water) ora saturated aqueous solution of sodium carbonate. The edge of theexposed to unexposed region was readily discernable in the resin.

[0133] The developed resin was dried and post cured at 125° C. for 2hours followed by 175° C. for 2 hours. The curing was monitored byFourier Transform Infrared (FTIR) spectroscopy, observing the allylgroup peak at 915 cm⁻¹ and the imide group peak at 1700 cm⁻¹ todiminish. The resultant resin was gelled and the edge of the exposedregions were clearly discernable.

[0134] Preferred applications for the inventive resin composition areillustrated in FIGS. 8-13. FIG. 8 shows a flip chip or ball grid arraydevice 1 which has electrical interconnection pads 2 on its surface. Thepads are encapsulated with a layer of the inventive resin 3. Microvias 4are created in the encapsulating resin layer 3 to expose the electricalinterconnection pads 2 as shown in FIG. 9 and FIG. 10 shows that themicrovias have been filled with electrically conductive interconnectmaterial 5 e.g., solder.

[0135]FIG. 11 shows a printed circuit board 6 having electricalinterconnections pads 7 where the board 6 is encapsulated with a layerof the inventive resin composition 8. FIG. 12 the presence of microviaopenings 9 in the encapsulating resin layer to expose the electricalinterconnection pads 6. Finally, FIG. 13 shows the printed circuit board6 wherein the microvias 9 and surface of the encapsulant 8 have beenplated with electrically conductive interconnect material 10 e.g.,copper. As illustrated the device has a patterned of the electricallyconductive interconnect material that produces selected electricalinterconnections between various microvias 11.

[0136] Although only preferred embodiments of the invention arespecifically disclosed and described above, it will be appreciated thatmany modifications and variations of the present invention are possiblein light of the above teachings and within the purview of the appendedclaims without departing from the spirit and intended scope of theinvention.

What is claimed is:
 1. A curable composition that comprises: (a) acyanate ester; (b) a bismaleimide; (c) a co-curing agent having thestructure R¹—Ar—R² wherein Ar is at least one unsaturated aromaticcarboxylic moiety, R¹ is at least one unsaturated aliphatic moiety, R²is at least one glycidyl moiety with the proviso that when two or moreunsaturated aromatic carboxylic moieties are present, at least one ofthe unsaturated aromatic carboxylic moieties has an unsaturatedaliphatic moiety and an epoxide moiety attached thereto; (d) an epoxyresin; and (e) optionally, a free-radical initiator.
 2. The compositionof claim 1 wherein the co-curing agent is selected from the groupconsisting of compounds having the structures I, II:

wherein each of R¹ and R² are each selected from H, —CH₃ or CF₃, andmixtures thereof.
 3. The composition of claim 1 wherein the co-curingagent is selected from 2-allyphenyl glycidyl ether, 2,2′-diallybisphenolA diglycidyl ether, and mixtures thereof.
 4. The composition of claim 1the cyanate ester is selected from the group consisting of compoundshaving the structures I, II, III:

wherein x is a divalent moiety, and mixtures thereof.
 5. The compositionof claim 1 wherein the cyanate ester is

wherein n is an integer from 0 to
 200. 6. The composition of claim 1wherein the resin composition does not include a solvent.
 7. Thecomposition of claim 1 wherein the epoxy resin is selected from thegroup consisting of bisphenol A based epoxy resin, bisphenol F basedepoxy resin, epoxy novolac, epoxy cresol novolac, triphenylomethanetriglycidyl ether, N,N-diglycydyl-4-glycidylpxyaniline, and4,4′-methylenebis(N,N-diglycidylaniline).
 8. The composition of claim 1comprising a heat triggered initiator.
 9. The composition of claim 1comprising an energetically triggered initiator.
 10. The composition ofclaim 1 further comprising a cyanate ester trimerization catalyst. 11.The composition of claim 1 wherein the cyanate ester comprises about 1.5to 5 molar equivalent parts of the composition, the bismaleimidecomprises about 0.5 to 1.5 molar equivalent parts of the composition,the co-curing agent comprises about 0.5 to 1.5 molar equivalents of thecomposition, and the epoxy resin comprising about 1.5 to 5 molarequivalent parts of the composition.
 12. The composition of claim 1wherein the epoxide molar equivalent concentration in the resincomposition is equal to or less than the cyanate ester molarconcentration.
 13. The composition of claim 1 wherein the co-curingagent molar equivalent concentration is less than the lesser of either(i) the cyanate ester molar concentration or (ii) the bismaleimide molarconcentration.
 14. A process of forming vias in a polymer compositioncomprising the steps of: (a) applying a layer of a resin compositionthat comprises (i) a cyanate ester; (ii) a bismaleimide; (iii) aco-curing agent having the structure R¹—Ar—R² wherein Ar is at least oneunsaturated aromatic carboxylic moiety, R¹ is at least one unsaturatedaliphatic moiety, R² is at least one glycidyl moiety with the provisothat when two or more unsaturated aromatic carboxylic moieties present,at least one of the unsaturated aromatic carboxylic moieties has anunsaturated aliphatic moiety and an epoxide moiety attached thereto;(iv) an epoxy resin; and (v) a radiation triggered free-radicalinitiator; (b) covering the layer of resin composition with a maskhaving windows through which radiation can be transmitted; (c) exposingpart of the resin composition to radiation to at least partially curethe resin composition in exposed areas; (d) removing non-cured portionsof the resin composition; and (e) completing the cure of the resincomposition.
 15. The process of claim 14 wherein the co-curing agent isselected from the group consisting of compounds having the structures I,II:

wherein each of R¹ and R² are each selected from H, —CH₃ or CF₃ andmixtures thereof.
 16. The process of claim 14 wherein the co-curingagent is selected from 2-allyphenyl glycidyl ether, 2,2′-diallybisphenolA diglycidyl ether, and mixtures thereof.
 17. The process of claim 14the cyanate ester is selected from the group consisting of compoundshaving the structures I, II, III:

wherein x is a divalent moiety, and mixtures thereof.
 18. The process ofclaim 14 wherein the cyanate ester is

wherein n is an integer from 0 to
 200. 19. The process of claim 14wherein the resin composition does not include a solvent.
 20. Theprocess of claim 14 wherein the epoxy resin is selected from the groupconsisting of bisphenol A based epoxy resin, bisphenol F based epoxyresin, epoxy novolac, epoxy cresol novolac, triphenylomethanetriglycidyl ether, N,N-diglycydyl-4-glycidylpxyaniline, and4,4′-methylenebis(N,N-diglycidylaniline).
 21. The process of claim 14wherein the resin composition comprises a heat triggered initiator. 22.The process of claim 14 wherein the resin composition comprises anenergetically triggered initiator.
 23. The process of claim 14 furthercomprising a cyanate ester trimerization catalyst.
 24. The process ofclaim 14 wherein the cyanate ester comprises about 1.5 to 5 molarequivalent parts of the composition, the bismaleimide comprises about0.5 to 1.5 molar equivalent parts of the composition, the co-curingagent comprises about 0.5 to 1.5 molar equivalents of the composition,and the epoxy resin comprising about 1.5 to 5 molar equivalent parts ofthe composition.
 25. The process of claim 14 wherein the epoxide molarequivalent concentration in the resin composition is equal to or lessthan the cyanate ester molar concentration.
 26. The process of claim 14wherein the co-curing agent molar equivalent concentration is less thanthe lesser of either (i) the cyanate ester molar concentration or (ii)the bismaleimide molar concentration.
 27. An electrical componentassembly, comprising: (a) an electrical component having a plurality ofelectrical terminations; (b) a component carrying substrate having aplurality of electrical terminations corresponding to the terminationsof the electrical component; and (c) a thermally curable adhesivecomposition that comprises: (i) a cyanate ester; (ii) a bismaleimide;(iii) a co-curing agent having the structure R¹—Ar—R² wherein Ar is atleast one unsaturated aromatic carboxylic moiety, R¹ is at least oneunsaturated aliphatic moiety, R² is at least one glycidyl moiety withthe proviso that when two or more unsaturated aromatic carboxylicmoieties are present, at least one of the unsaturated aromaticcarboxylic moieties has an unsaturated aliphatic moiety and an epoxidemoiety attached thereto; (iv) an epoxy resin; and (v) optionally, afree-radical initiator.
 28. The electrical component assembly of claim27 wherein the co-curing agent is selected from the group consisting ofcompounds having the structures I, II

wherein each of R¹ and R² are each selected from H, —CH₃ or CF₃, andmixtures thereof.
 29. The electrical component assembly of claim 27wherein the co-curing agent is selected from 2-allyphenyl glycidylether, 2,2′-diallybisphenol A diglycidyl ether, and mixtures thereof.30. The electrical component assembly of claim 27 the cyanate ester isselected from the group consisting of compounds having the structures I,II, III:

wherein x is a divalent moiety, and mixtures thereof.
 31. The electricalcomponent assembly of claim 27 wherein the cyanate ester is

wherein n is an integer from 0 to
 200. 32. The electrical componentassembly of claim 27 wherein the composition does not include a solvent.33. The electrical component assembly of claim 27 wherein the epoxyresin is selected from the group consisting of bisphenol A based epoxyresin, bisphenol F based epoxy resin, epoxy novolac, epoxy cresolnovolac, triphenylomethane triglycidyl ether,N,N-diglycydyl-4-glycidylpxyaniline, and4,4′-methylenebis(N,N-diglycidylaniline).
 34. The electrical componentassembly of claim 27 wherein the resin composition comprises a heattriggered initiator.
 35. The electrical component assembly of claim 27wherein the resin composition comprises an energetically triggeredinitiator.
 36. The electrical component assembly of claim 27 wherein theresin composition further comprises a cyanate ester trimerizationcatalyst.
 37. The electrical component assembly of claim 27 wherein thecyanate ester comprises about 1.5 to 5 molar equivalent parts of thecomposition, the bismaleimide comprises about 0.5 to 1.5 molarequivalent parts of the composition, the co-curing agent comprises about0.5 to 1.5 molar equivalents of the composition, and the epoxy resincomprising about 1.5 to 5 molar equivalent parts of the composition. 38.The electrical component assembly of claim 27 wherein the epoxide molarequivalent concentration in the resin composition is equal to or lessthan the cyanate ester molar concentration.
 39. The electrical componentassembly of claim 27 wherein the co-curing agent molar equivalentconcentration is less than the lesser of either (i) the cyanate estermolar concentration or (ii) the bismaleimide molar concentration.
 40. Aprocess of forming vias in a polymer composition comprising the stepsof: (a) applying a layer of a resin composition that comprises: (i) acyanate ester; (ii) a bismaleimide; (iii) a co-curing agent having thestructure R¹—Ar—R² wherein Ar is at least one unsaturated aromaticcarboxylic moiety, R¹ is at least one unsaturated aliphatic moiety, R²is at least one glycidyl moiety with the proviso that when two or moreunsaturated aromatic carboxylic moieties are present, at least one ofthe unsaturated aromatic carboxylic moieties has an unsaturatedaliphatic moiety and an epoxide moiety attached thereto; (iv) an epoxyresin; and (v) optionally, a free-radical initiator; (b) covering thelayer of resin composition with a mask having openings through whichradiation can be transmitted; (c) exposing part of the resin compositionto radiation to at least partially cure the resin composition in exposedareas; (d) removing non-cured portions of the resin composition; and (e)completing the cure of the resin composition.
 41. The process of claim40 wherein the co-curing agent is selected from the group consisting ofcompounds having the structures I, II:

wherein each of R¹ and R² are each selected from H, —CH₃or CF₃ andmixtures thereof.
 42. The process of claim 40 wherein the co-curingagent is selected from 2-allyphenyl glycidyl ether, 2,2′-diallybisphenolA diglycidyl ether, and mixtures thereof.
 43. The process of claim 40the cyanate ester is selected from the group consisting of compoundshaving the structures I, II, III:

wherein x is a divalent moiety, and mixtures thereof.
 44. The process ofclaim 40 wherein the cyanate ester is

wherein n is an integer from 0 to
 200. 45. The process of claim 40wherein the resin composition does not include a solvent.
 46. Theprocess of claim 40 wherein the epoxy resin is selected from the groupconsisting of bisphenol A based epoxy resin, bisphenol F based epoxyresin, epoxy novolac, epoxy cresol novolac, triphenylomethanetriglycidyl ether, N,N-diglycydyl-4-glycidylpxyaniline, and 4,4′-methylenebis(N,N-diglycidylaniline).
 47. The process of claim 40wherein the resin composition comprises a heat triggered initiator. 48.The process of claim 40 wherein the resin composition comprises anenergetically triggered initiator.
 49. The process of claim 40 furthercomprising a cyanate ester trimerization catalyst.
 50. The process ofclaim 40 wherein the cyanate ester comprises about 1.5 to 5 molarequivalent parts of the composition, the bismaleimide comprises about0.5 to 1.5 molar equivalent parts of the composition, the co-curingagent comprises about 0.5 to 1.5 molar equivalents of the composition,and the epoxy resin comprising about 1.5 to 5 molar equivalent parts ofthe composition.
 51. The process of claim 40 wherein the epoxide molarequivalent concentration in the resin composition is equal to or lessthan the cyanate ester molar concentration.
 52. The process of claim 40wherein the co-curing agent molar equivalent concentration is less thanthe lesser of either (i) the cyanate ester molar concentration or (ii)the bismaleimide molar concentration.